Test elements for analyzing aqueous solutions are generally known. For example, test elements for analyzing pool or spa water typically include three chemically treated pads arranged on a substrate; one for measuring free chlorine or bromine concentration, one for measuring pH level and one for measuring total alkalinity of the pool or spa water. To analyze the pool or spa water, such a test element is typically exposed to the pool or spa water, and a chemical reaction then takes place between the chemicals on each of the pads and the pool or spa water. This causes each of the pads to change to a color that is indicative of the corresponding pool or spa water characteristic. The colors of the pads are then typically compared visually to a color chart that maps pad color to a corresponding pool or spa water characteristic.
Test elements are also known for analyzing blood and urine samples. U.S. Pat. No. 5,304,468 describes a test strip and apparatus for determining blood glucose levels by measuring the reflectance of the test strip. The test strip is placed in a detector and a removable cover is then closed to shield the assembly from ambient light. The test strip is illuminated by an LED and the reflectance is measured and correlated to a blood glucose level. The device is calibrated for variations in LED brightness by placing the test into the device prior to it being wetted with blood, and adjusting power to the LED if the reflectance is different than a predetermined value. Because the red color of blood can interfere with the accuracy of the measurement, measurements are taken at two wavelengths in order to permit a first order subtraction of the background color of the blood. Furthermore, two wavelength readings permit a second order correction to eliminate chromatography effects resulting from variations in the hematocrit levels among various blood samples. Such devices are inconvenient to use and may be prone to inaccurate results if the cover becomes inoperative or if the user elects not to take the time to perform the pre-wetting calibration step.
U.S. Pat. No. 6,979,571 describes another test strip reader wherein a protective shroud is used to separate the test strip from the optics of the device. The shroud is provided with a hood, camming members and fingers for guiding the test strip into a groove formed in the shroud to align the test strip with the device optics. Such devices are expensive to manufacture, inconvenient to use, and vulnerable to mechanical failure due to the precision location necessary for the fingers and camming members.